Chinese submarine crossed into territorial waters close to Taiwan’s largest naval base last week, reports said Sunday.

The unidentified vessel was moving just 24 nautical miles southwest from the Tsoying base in Kaohsiung last Wednesday morning as Taiwan’s navy was holding maneuvers close by, the Chinese-language United Evening News reported. A Navy spokesman denied the newspaper story later Sunday.

The submarine first appeared on the sonar of a Taiwanese S-70C anti-submarine helicopter. The Taiwanese frigates on a drill nearby were put on full alert and joined the search. The submarine never responded to requests and left the area shortly later,...